#define _CRT_SECURE_NO_WARNINGS	

#include<stdio.h>

int main()
{
    int n;
    scanf("%d", &n);
    double s = 1;
    for (int i = 2; i <= n; i++)
    {
        s -= 1.0 / i;
    }
    printf("%.6lf", s);
    return 0;
}
